The present invention relates to computerized tomography systems and more particularly, to a computerized tomography system and method which can suitably take a tomographic image in a transversal plane of an object to be inspected with use of X ray.
A computerized tomography system (X-ray computed tomography (CT) system or X ray CT system) using X ray, which takes a tomographic image in a transversal plane of an object to be inspected, includes an X ray source for emitting an X ray, a detection device for detecting the X ray and a computer for creating a tomographic image. In particular, the detection device comprises, in many cases, an array detection device made up of a multiplicity of X ray detectors arrayed in a row. The X ray detectors of the array detection device are arranged to detect the X ray emitted from the single X ray source. In such an X ray CT system, especially employing a tomography called a third generation system, in order to increase the spatial resolution of a tomographic image, it is necessary to narrow an array interval or pitch between the X ray detectors of the array detection device.
However, the array detection device has its limitation on making narrow the array pitch between the X ray detectors of the array detection device, because the X ray detectors have a limited size. For example, when each X ray detector has a transverse width of 1 mm, it is impossible to make the pitch between the X ray detectors of the array detection device to be 1 mm or smaller. Accordingly, there has been demanded such a tomography system which can increase the spatial resolution of a tomographic image while eliminating the need for narrowing the array pitch between the X ray detectors of the array detection device.
In such an X ray CT system disclosed in JP-A-62-116238, a relative positional relationship between an X ray source and an array detection device is made variable in a range of interval or pitch between X ray detectors of the array detection device, thus enabling increase of a spatial resolution of an tomographic image while eliminating the need for physically narrowing the array pitch of the X ray detectors.
In the case of an X ray CT system wherein a collimator having slits for passage of an X ray is provided in front of the X ray detectors of the array detection device (on a side of an X ray source), however, it is impossible to employ such a technique as disclosed in the above JP-A. This is because the slits provided in front of the X ray detectors are positioned to face the single X ray source, so that a shift in the relative positional relationship between the X ray source and X ray detectors causes the X ray not to be directed on the X ray detectors.